By: Jill Detwiler, Water Resources Coordinator at the Clinton Conservation District
People who work with plants have first-hand experience dealing with limiting nutrients. For example, a deficiency in available nitrogen may result in corn that is low-yielding, chlorotic, and stunted, despite all other nutrients being available to the crop. Nitrogen is called the “limiting nutrient” in this example because its insufficiency is what limits the growth of the corn.
Of course, soil amendments are used to help overcome nutrient limitations. It’s important to note, however, that plants only need certain amounts of nutrients to meet their needs. Excess nutrients will be lost through surface runoff, erosion, groundwater discharge, or atmospheric losses.
The concept of limiting nutrients also exists in natural systems such as lakes, streams, and wetlands. Phosphorus (P) is often the limiting nutrient in aquatic ecosystems. Usually, phosphorus is naturally present in amounts that support the growth and development of native aquatic plants, but in moderation. Excess amounts of P – entering waterways predominately due to human activities – promotes the growth of algal blooms. Large algal blooms can have devastating impacts on our water resources by creating low dissolved oxygen conditions in waterbodies (a process called eutrophication) which harms or kills aquatic wildlife and producing harmful toxins that impair drinking water sources. Major sources of P pollution include fertilizer and manure runoff, failing septic systems, and sewage treatment plants.
Phosphorus pollution is present in several reaches of the Maple River Watershed. This has led to the establishment of Total Maximum Daily Load (TMDL) requirements for phosphorus set by the US EPA. P pollution is impairing portions of the Maple River Watershed’s ability to support a warm water fishery, and it is also negatively impacting important habitat for native wildlife and aquatic macroinvertebrates.
Growers have several options for helping prevent phosphorus from entering waterways. Soil testing is one important and affordable option that helps prevent the over-application of nutrients. Other options include planting buffer strips along waterways (like county drains), tile control structures, and cover crops. These practices help capture nutrients from running off into waterways. The bonus of cover crops is that some of the captured nutrients are recycled to the field when cover crops decompose and are used by next year’s cash crop. Also, homeowners with septic systems are reminded to have tanks and drain fields inspected every 3-5 years to make sure no leaks are occurring.
The Clinton Conservation District has several cost-share funding options for farming practices that promote water conservation. Call our office at (989) 224-3720 to learn more about our programs.